still new at this, but have taken over care of an established tank. My ph readings are right around 7.7 to 8.0. I'm not a good judge of color but my husband's opinion is 8.0, I see it as 7.7 or 8.0 but think I'm seeing a decrease over time. Should I try a chemical increaser? The previous owner gave me some PH increaser that says for freshwater, not sure if he ever used it for the saltwater or if it was for a different tank. I'm not sure the most practical method of adding a chemical - would I add it to my next water change?

I read something about increasing the circulation in the water bringing it back up - any opinions on that method?

Have a couple of questions? What time of day did you measure pH? Do you have a glass top on the tank? What type of water are you using?
Each of these can have an effect on the pH.
increasing circulation and breaking water surface (ripples or splash) can increase pH if CO2 build up is cause of lower pH.

Marine buffers can also increase ph and alk. After more info is provided (test parameters for CA and dKH) we can help you better. Until then try more surface agitation (if there isn't any) and use eggcrate as a cover for the tank rather than glass (helps gas exchange).

I suspect the tank hasn't had good water changes in recent months (from the way you describe having to 'take over the care of the tank'). I suspect alkalinity is low, causing a low pH.
You need an alkalinty/Carbonate hardness test kit. Run the test and report the results back here.

__________________Former advisor and planted tank geek...life's moved on though.

We are using RO water and adding our own salt. I measure the ph around 2:30 on Thursdays. I have an oak top on it now that is open on the wall side. We had to add it to keep my toddler from throwing things into the tank! We do change the water frequently. When we first got it we waited about three weeks but now we are doing weekly changes. We have a wavemaker and a maxijet pump. We have an extra little pump we put in for a little while but it seemed like it was stirring up the sand so we took it out. From these posts I'm thinkin we should put it back in close to the surface? We also added a fan but I've only been running it on hot days, should I run it more? I will do the alk/hardness test when the kids are in bed. It might be tomorrow before I can post but I will get it done.

__________________
fourmyclowns ....and my four boys who are the real clowns!

Okay, tested the KH (carbonate hardness) and I did the more accurate test using 10ml tank water (1drop testing fluid=1/2'dH) . It took me 15 drops. If I understand it right that would equal 7.5dH. Does that mean our water is TOO hard?

Malkore's post said:
"You need an alkalinty/Carbonate hardness test kit. Run the test and report the results back here"
Is this test one test (the one I just did) or should I be looking for an additional one that specifically says "alkalinity"? I still need to go buy the Calcium test but that will have to happen tomorrow late in the day.

7.5 DKH is a fine level and will maintain pH properly. The issue is aeration, not chemistry. Add an additional powerhead at the surface (heavy surface rippling without splashing) and keep the fan in the hood running all the time. This will help bring up the pH naturally. It will also increase evaporation so have top off water ready each day.

The only time you want to use a higher alk level is when correcting environmental issues are ineffective. Even then, chemical means are merely a bandaid and will continue to be a problem.